anaphylatoxin

Originally used of an antigen that reacted with an IgEantibody thus precipitating reactions of anaphylaxis. Now restricted to defining a property of complement fragments C3a and C5a, both of which bind to the surfaces of mast cells and basophils and cause the release of inflammatory mediators.

anaphylatoxin — Low molecular weight substances generated by the activation of complement; the biologically active complement components are derived from C3, C4, and C5 and lead to increased vascular permeability as a result of the degranulation of primarily… … Medical dictionary

anaphylatoxin — noun Any of several toxic substances that trigger anaphylaxis … Wiktionary